1. Field of the Invention:
The present invention relates to a sequence control monitoring device capable of automatically monitoring the operating states of controlled-objects in a sequence control system.
2. Description of the Prior Art:
A sequence control system often involves maintenance problems, For instance, in the event of failure of a controlled-object, such as a limit switch or solenoid valve, maintenance personnel have had to visually or manually detect the location of the failure, relying heavily on their skill and experience. In practice, the point of failure cannot always be detected with ease, depending upon the skill and experience of maintenance people, as well as upon the location at which the controlled-object is installed. A need therefore exists for an automatic monitoring system for detecting such failures rapidly and accurately.